The present invention relates to MEMS capacitive microphones and processing systems for the same. MEMS capacitive microphones operate utilizing conservation of charge. A high impedance switch network, usually consisting of two anti-parallel diodes with a MOS transistor in parallel with the diodes, is used to apply a fixed charge across two plates of a capacitor. When the microphone is initially turned on the MOS transistor is switched on allowing a DC voltage to be put on one plate of the capacitor while the other plate is held at a different electrical potential. When the capacitor is fully charged (typically within 10's of milliseconds) the MOS transistor is switched off and the capacitor is left with a fixed charge across the two plates. When sound pressure waves impinge on the moveable plate of the capacitor, the capacitance changes and, because the charge is fixed across the capacitor, the voltage increases or decreases proportionally to the amount of change in capacitance induced by the incident sound pressure.